Web service (WS) technologies have recently attracted an explosive interest and are sometimes said to be revolutionizing the packet-based communication networks. A web service is basically a network accessible interface to application functionality implemented through standard Internet technologies. By means of web services, one piece of software can access objects and methods from another piece of software irrespective of long distances and intermediate firewalls, which allows for distributed software systems.
Three ways have been proposed for introducing web services in mobile networks. These architectures will gradually be introduced in the network and in due time all three may co-exist. In a first WS scenario, the user accesses the application through a web page in the browser. The application is located on a web server and interacts with web services to prepare the response back to the browser. Many of today's enablers (location, charging, etc.) will introduce web services in this manner. Secondly, there can be direct access to web services from the mobile device. In this case, a web service enabled application in the mobile device communicates directly with web services on the web. Finally, in a third scenario, the web services are located at mobile devices. A mobile device requests a web service located at another mobile device. The web service utilization then relies on peer-to-peer connections and this is the scenario addressed herein.
Connectivity between mobile devices can be achieved in different ways. One way would be to have full IP connectivity in the mobile network, but due to security and payment considerations this would not be feasible. Also, in IPv4, the number of public addresses would not be enough. The normal way to achieve peer-2-peer connections is instead to introduce an overlay network, such as the IP Multimedia Subsystem (IMS). IMS provides IP services independent of applications and platforms.
IMS uses the Session Initiation Protocol (SIP) as session control mechanism. SIP is indifferent to media and defines how a connection should be handled irrespective of whether the content is voice, video, data or web-based. By means of SIP, mobile devices can be registered and peer-to-peer connections initiated. A conventional registration via IMS/SIP is a registration of the SIP client of the mobile device. All SIP messages to a particular end user are (via the IMS infrastructure) sent to the SIP client in the user device.
Prior-art solutions like the above IMS/SIP registration are not very well suited for handling web services located in mobile terminals. Such situations are often rather complex, in particular since there may be more than one web service at each mobile node and more than one end user that wishes to purchase the same web service, and there is a considerable need for appropriate mechanisms for handling web services in mobile peer-to-peer systems.